Conventional semiconductor device manufacturing plants are generally large in scale for relying on the mass production to reduce production costs. For example, one known manufacturing plant is capable of producing 1,000 lots (one lot includes 100 wafers) per month. In such a large scale plant, there are installed more than several hundred main apparatuses (equipments), and it would typically include more than one hundred points of use which are processing facilities that use pure water for processing.
FIG. 1 illustrates a pure water supply system which is an example of conventional material supply system. A pretreatment equipment 1 introduces a coagulants and the like into raw water, filters the raw water to remove turbid components included in the raw water, and stores the filtered water in a filtered water tank 2. Next, a primary pure water system 3 mainly removes ion components included in the filtered water from the pretreatment equipment 1 (and recovered water from a recovery system 7) to produce primary pure water which is stored in pure water tank 4. Next, an ultrapure water system (i.e., a subsystem) 5 further refines the primary pure water from the primary pure water system 3 to produce ultrapure water. The ultrapure water is supplied to a variety of points of use 6 in a semiconductor device manufacturing plant. Dilute waste water such as rinse water from the points of use 6 is recovered by the recovery system 7, and partially stored in the filtered water tank 2, depending on the condition of the recovered water, for reuse in the primary pure water production in the primary pure water system 3, and partially stored in a reuse tank 8 for reuse in the facilities of the plant as appropriate. Waste water other than the dilute waste water exhausted from the points of use 6 is processed in a waste water processing system 9 before it is emitted. In this event, solid components in the waste water are dehydrated and wasted as sludge.
The ultrapure water produced in the foregoing manner is supplied to all the points of use 6.
In the following description, the “primary pure water” and “ultrapure water” are represented by “pure water” when they are collectively referred to.
In recent years, however, semiconductor products have been increasingly required in a wider number of applications, including products for personal computers to digital electric appliances such as portable telephones, but they tend to have shorter life cycles. To meet this trend, a shift has been made from mass production to flexible production in the production of semiconductor products, and moreover, the production is required to be agile. A production method proposed to meet the requirements is a small-scaled semiconductor device manufacturing plant (hereinafter called the “small-scaled plant”). The small-scaled plant, however, is required to be as cost-competitive as a large-scaled semiconductor device manufacturing plant (hereinafter called the “large-scaled plant”), in addition to the requirement that it be capable of flexible production.
In regard to a pure water supply system in the small-scaled plant, a simple reduction in scale of the pure water supply system generally installed in a large-scaled plant would cause an increase in the production cost of pure water per unit (initial cost and running cost) which is reflected to a production cost of semiconductor products.
Such problems implied in the small-scaled plant are not limited to the supply of pure water, but may apply to the supply of materials such as material gases and chemicals for use in processing of semiconductor wafers, gases and liquids for washing processing facilities, cooling water for pumps associated with the processing facilities and heaters for heating reaction chambers, and the like.
On the other hand, in conventional semiconductor device manufacturing processes, a variety of processing facilities in the plant use numerous material gases, chemicals and solvents as required by particular processes. These materials are generally supplied from cylinder cabinets, gas generators, storage tanks for storing chemicals and solvents, and refiners such as ion exchangers through gas pipes or chemicals pipes routed over the plant, respectively. The supply facilities such as the cylinder cabinets, gas generators, storage tanks for storing chemicals and solvents, refiners such as ion exchangers, and the like must be sufficient in scale to appropriately support the plant in terms of consumption rates of the gases, chemicals and the like used therein. This requirement must be applied not only to the supply capabilities of the supply facilities but also to inner diameters of pipes, through which the materials are transported to respective manufacturing apparatuses associated therewith, in conformity to the consumption rates.
However, in the processing facilities, these material gases, chemicals and the like are not always consumed at the same rate. For example, in an LPCVD furnace in which a polycrystalline silicon film is deposited on a plurality of substrates in batches by LPCVD, the LPCVD furnace is supplied with a monosilane gas, which is the material of the silicon film, only when the silicon film is being deposited. Thus, although no monosilane gas is consumed when the furnace is evacuated, when semiconductor wafers are carried on shelf-like boards for processing, and the like, the supply capability of an associated supply facility, and the transport capability of associated piping are designed based on the flow rate of the monosilane gas when it is being consumed. When ten such LPCVD equipments are installed in a plant, the supply facilities and transport facilities are provided for the ten equipments. Not limited to those materials which are consumed directly in relation to the processing of semiconductor wafers, such as the monosilane gas, cooling water for a heater is required only when the heater is operated for heating, and less water is required when the heater is not operated.
Furthermore, the diameter of semiconductor wafers used in the semiconductor manufacturing processes tends to become larger year by year from a view point of production efficiency, and accordingly larger processing chambers are provided in the semiconductor manufacturing plant, causing an increase in the amounts of material gases and chemicals consumed therein. Eventually, large capacities are required to such supply facilities and transport facilities in order to supply required amounts of material gases, chemicals and the like, resulting in an increased investment on the facilities.
Thus, a serious problem exists not only in small-scaled plant but in large-scaled plant, namely, how to economically run a system for supplying material gases, chemicals and the like through a reduction in capacity.